1. Field of the Invention
This invention relates to a new and improved stripping solution. More particularly, the invention relates to a new type of stripping solution which not only rapidly removes coatings from coated substrates but also conditions the substrate for subsequent coating treatments.
Specifically, the invention provides a new and improved stripping solution which is effective in removing all types of coatings from coated substrates and conditioning the resulting substrate for immediate coating with other materials, which new stripping solutions are obtained by mixing in special proportions (1) a solvent composition comprising a chlorinated solvent and a liquid alcohol containing at least three carbon atoms, (2) a wetting composition comprising basic metal ammonium salt of an aromatic sulfonic acid, and a non-ionic surface active material, and (3) a vapor suppressant, and said mixture preferably containing a small amount of water. A method for using these solutions for stripping and conditioning coated substrates, and particularly metal substrates, is also disclosed.
2. Prior Art
There is a need in industry for compositions which can be used to strip coatings from substrate, such as metal and wood. This is particularly needed for the treatment of automobiles, buses, trucks, trains, boats, etc. which often require recoating because of extensive use.
The development of a satisfactory stripping solution is particularly difficult because of the great variety of coatings and substrates now in use in industry. The automotive industry uses a wide variety of coating systems, including electro-deposition primers (anodic-acrylic/cathodic epoxy), epoxy ester primers, acrylic lacquers, urethane and thermosetting acrylic enamel topcoats. Each of the major suppliers of original finishes have proprietary systems which can vary in composition and cross-linking density. Such coatings may be baked or air-dried.
The refinish market servicing the automotive, truck and aircraft industry also adds another myriad of systems including polyurethane and acrylic-urethanes. The substrate can vary from plastic (polyester, polyurethane, ABS) to metal (e.g. magnesium, aluminum, galvanized metal, cold rolled steel, etc.). The metal surfaces may be treated with phosphate to prevent rusting or chromated to passivate zinc or aluminum oxides.
One solution to the problem in the past has been to use sand blasting in removing the great variety of coatings. This has not been satisfactory, however, because of the dusty conditions involved, time consumed and the removal or damage of the surface of the substrate.
Attempts have been made to solve the problem by developing chemical solutions which could be used to strip the coatings from the substrate. The ideal stripping solution would be one that would be universally effective in removing all types of coatings and primer systems, would effect the stripping in a short period, and would require only one application of the solution. In addition, the stripping solution should leave the substrate, after final washing and rinsing, in such condition that it could be immediately recoated without additional treatment, such as phosphatizing or anodizing the said substrate. Finally, the ideal stripping solution would be one that is non-toxic or corrosive and could be easily disposed of after use.
The attempts to prepare such an ideal stripping solution have not been too successful in the past. Some of the stripping solutions developed have been effective against some types of coatings but ineffective against others. Some are effective only after numerous applications or after long periods of exposure to the stripping solutions.
A further defect of known stripping solutions, and one that is particularly important from a practical standpoint is that they all leave the stripped substrate in such condition that considerable treatment is required because it can be recoated. The prior known stripper compositions are acidic or basic activators and act by means of blistering, dissolving and otherwise removing the coatings. None of these known compositions act both as a stripper and a metal conditioner for subsequent coating treatment. A composition which would effect both a stripping and conditioning action would be a significant contribution to the art.
In addition, the prior known stripping compositions have been limited as they have had obnoxious odors and contain phenolics or acids and are hard to handle because of skin irritation. Others have not been biodegradable and disposition has been a problem.
Patents which disclose stripping compositions which have many of the above-noted defects include:
U.S. Pat. Nos. 2,443,173, 2,969,328, 3,650,969, 4,285,827, 3,106,929, 3,957,530, 3,979,219, 3,983,047, 3,988,256, 4,296,724.
It is an object of the invention, therefore, to provide a new and improved stripping solution. It is a further object to provide a new solution which acts both to remove the coating as well as condition the stripped substrate for subsequent coating treatment. It is a further object to provide a stripping and conditioning solution which is effective against all known coatings and primer compositions. It is a further object to provide a stripping and conditioning solution which is effective in a very short period of time even at normal temperatures and is effective even with one application of the solution. It is a further object to provide a stripping and conditioning solution which is non-corrosive and non-toxic and biodegradable. It is a further object to provide a stripping and conditioning solution which is economical to prepare and easily utilized. These and other objects of the invention will be apparent from the following detailed description thereof.